The Transportation Security Administration is looking to increase the number of full-body scanners at U.S. airports over the next few years as it reviews security procedures in the wake of the attempted bombing of a Northwest Airlines flight last week.

Experts say a full-body scanner likely would have detected the powdered explosive that terror suspect Umar Farouk Abdulmutallab allegedly stuffed in his underwear and ignited aboard a flight from Amsterdam to Detroit on Christmas.
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The full-body scanners allow TSA officials to look under clothing for any contraband — for instance, the PETN explosive sewn into the underwear of the alleged would-be bomber last week — but there are relatively few in operation now. Nineteen airports in the U.S. are using a total of 40 of the scanners. Only six airports use the scanners as their primary method of screening.

But Gaches said TSA has purchased and received 150 more of the machines, and it plans to distribute them next year. The agency plans to purchase 300 more next year, at a cost of between $130,000-$170,000 per unit.

But the machines, which can “see” through clothing and reveal the shape of a passenger’s body, have raised privacy concerns and are currently optional. Any passenger who doesn’t want to go through a full-body scanner is allowed to request a pat-down instead.